Multi-layer composite materials are used in the field of packaging, after they have been cut, folded and glued. One of these composites commonly used is corrugated board. It is used mainly as a protective packaging that is particularly strong while being readily recyclable.
Corrugated board is for example made up of an inner board provided with flutes, bonded onto a first flat coverboard on one side of the flutes. This inner board with first flat coverboard constitutes a single-face corrugated board. The single-face corrugated board obtained is also bonded, i.e. laminated, with a second flat board on the other side of the flutes.
To make the packaging more attractive, the corrugated board is often modified, for example printed matter is printed on it. This operation is performed by flexography in order to obtain quality prints in multiple colours. However, printed corrugated board may exhibit defects, for example in the case of relatively thin corrugated board. The defects are not acceptable for packaging for expensive products.
Some printing defects among others are lines corresponding to each tip of the flutes because, during printing, the corrugated board will be crushed slightly. The difference in strength between the tips of the flutes and the regions separating two consecutive flute tips is the main reason why these lines appear during the printing operation.
For avoiding these defects, one technique then is to use laminating to assemble a sheet-like element in the form of a pre-modified for example preprinted sheet of board, onto a backing in the form of a single-face corrugated board or single-face corrugated web. Another technique is to use laminating to assemble a first web in the form of a first preprinted solid board web, onto a second web in the form of a second single-face corrugated board web.
The manufacture of a corrugated cardboard according to the second technique is carried out by means of a laminating machine which includes, upstream to downstream:                a first feeding unit for the first web, the first web coming from a first reel,        a second feeding unit for the second web, the second web coming from a second reel,        a gluing unit for the glue coating, in which a device deposits a layer of glue for example on the tip of the flutes of the second web,        a laminating unit for the junction and for the gluing of the first web on the second web, i.e. on the tips of the single-face corrugated web,        devices for longitudinal and transverse cutting of the composite obtained, for example of the corrugated web obtained, and        a delivery unit for cardboard sheets cut at the requested format.        
If the second web is a single-face corrugated board, it could also be produced in line with a corrugator, which is placed upstream of the laminating machine.
In usual production of corrugated board, the glue is starch-based glue. This glue requires a heating device inserted in the laminating unit into the production line. The glue is inexpensive and widely used for obtaining a strong fastening of the upper, intermediate fluted and lower layers together. However this glue is not adapted for the production of quality packaging sheets, as it penetrates the paper layers. The high content of glue leads to printings that include defects, such as spots or lines.
For obtaining a better quality, the producers use cold glue, for example a vinylic glue. Less penetration of this cold glue into the layer of the paper substrate on which it is coated occurs because it is not necessary to introduce additional heat. This avoids defects at the printed surface or surfaces of the end product. In the laminating unit, the gluing of cover sheets on the tip of the flutes requires also a significant supply of glue. Vinylic glue is, however, a costly glue.
In the known laminating unit, the lamination is performed at a convergence line situated between a top laminating roll and a bottom maintaining roll or a bottom vacuum table. A second, driven top roll is intended to pull the first web by squeezing it against the laminating roll. The first web and the laminating roll are driven by the second web which is itself longitudinally driven by a transport device such as a vacuum belt.
Slipping of the first web negatively affects the register of the printed first web to the printed second web. For instance, the printing on the surface of the first web does not correspond to the printing on the opposite surface of the second web. A production batch may be wasted by defects and be rejected.
Moreover for obtaining driving movement without sliding, delamination or pulling out of the first web with respect to the second web, the operator may increase the quantity of glue. The price of the packaging increases with a higher quantity of glue. On the other hand, if the quantity of glue is not sufficient, small sliding may occur, with the result that the strength of the composite obtained by the lamination decreases.